Abstract: This study proposes to examine (a) the longitudinal influence of physical activity on adolescent alcohol use, and (b) whether depressive symptomatology mediates the hypothesized relationship between physical activity and adolescent alcohol use. The central hypothesis to be tested is the influence of physical activity on alcohol use behaviors among adolescents through mediators such as depressive symptomatology. The research will be conducted using secondary data analysis drawn from The National Longitudinal Study of Adolescent Health (Add Health). A longitudinal design will be used in the proposed research. The sample will consist of 2718 adolescents in 8th grade at wave 1 followed to 9th grade one year later in wave 2. The sample will include equal numbers of males and females between the ages of 13 and 15 who participated in the Add Health data collection. The sample will be divided equally between genders in order to facilitate the research aim of exploring variations across genders in the way that depressive symptomatology mediates the relationship between physical activity and alcohol use behaviors. Participants will be from ethnically diverse backgrounds, therefore, ethnicity will be controlled for in the study. The analyses for the proposed research will include data collected from scales on physical activity participation, depressive symptomatology, and alcohol use. Structural equation modeling will be the primary method of data analysis for testing the relationship among variables in the proposed study. The proposed study fully compliments both my training and future career goals as a future independent researcher dedicated to preventing adolescent alcohol use and improving clinical practice through research. PUBLIC HEALTH RELEVANCE: Project Narrative: The proposed study aims to contribute understanding of how physical activity influences alcohol use behaviors among adolescents. Expanding upon prior research concerning the effects of physical activity participation on adolescent alcohol use, as well as the putative mediating role of depressive symptomatology during this period of growth and change could lead to prevention and intervention approaches in service delivery among adolescent populations. Furthermore this knowledge could inform research about specific behaviors that need to be targeted in prevention and treatment programs among adolescents.